That’s the question posed at Getting Rich Slowly. JD discusses that trend that many Americans are starting to dine out more because 1) it saves time, and 2) prices at restaurants are starting to go down (examples: the proliferation of $1 menus at fast food restaurants.)

But does dining out really save time or money? This calls for the scientific method.

As an experiment, Rob Cockerham spent all of February 2004 “eating in”, consuming only food from grocery stores. He calculated that he spent $11.55 per day on food and drink. (If you subtract alcohol, he spent $8.65 per day.) He spent 48 minutes per day preparing food.

During March 2004, Cockerham ateall of his meals in restaurants. He spent an average of $20.08 per day. (He also left just over $1 per day in tips.) But it didn’t just cost more money to eat out:

The big surprise, for me, was how long it took to eat out. It was easy, when I was eating in, to whip up many meals in less than 8 minutes, but it was almost impossible to get my food that fast when eating out.

There you have it, “eating in” not only saves money, but saves time.

I wasn’t surprised that it’s cheaper to save money; however, I was surprised that it saves time. But looking at the big picture it makes sense. At home, I can whip up a mean egg sandwich in less than 10 minutes. If I wanted the same thing at Sonic, I would have to drive 5 minutes to the restaurant, take 2 minutes to pick what I wanted even though I already knew I wanted an egg toaster, order, wait 5 minutes for my food to get there, take 2 minutes to scarf it down, and drive back home in 5 minutes. Total time: 22 minutes.

Sadly, my pathetic excuse for opting for the Sonic egg sandwich is that I hate cleaning up after cooking. It only takes two minutes, but I irrationally think that those two minutes are depriving me of study time. So, I go to Sonic instead, which ends up being the more irrational choice.

Lesson: Don’t eat out, when you can eat in. It is not only financially unfrugal, it completely unfrugal with your time.